The attack left Donaghy with chronic pain in his knee and in need of surgery, which may not be performed until he is released, Zaranek said.
"He wants to get out for obvious reasons, but he also needs to get the knee fixed," Zaranek said. "So, he doesn't want the fixing of the knee to forestall the release."
Federal Bureau of Prisons spokeswoman Traci Billingsley declined comment.
Donaghy reported to the camp in September. He said he took thousands of dollars from a professional gambler in exchange for insider tips on NBA games, including some he worked.
Zaranek didn't know the attacker's name but said he was removed from the camp at Saufley Field, a naval installation, while Donaghy was given protective status. He said reports on the attack will not be made public until Donaghy is released.
Donaghy, 42, expects to be transferred to a halfway house in Tampa on June 17 to complete his sentence, Zaranek said. He's scheduled for release on Oct. 24. Donaghy lived Bradenton, just south of Tampa, before he went to prison. His wife divorced him after his arrest. They have four daughters.
"He's very remorseful," Zaranek said. "He has a rather compelling story, and it rather tragically illustrates the destructive power of addiction to gambling."
While in prison, Donaghy has begun working on a tell-all book on "how he picked those winners 70 to 80 percent of the time and about the knowledge of the special relationships that exist between referees, players and coaches," Zaranek said.
"To understand his addiction, what transpired, you have to understand what led up to it during his 13 years in pro basketball and the whole culture of what he perceived as fraud and manipulation in the NBA," he said.